This invention relates to electrical connection fusing machines, and more particularly to machines for fusing the coil wires of an electric motor and insuring that the fusing electrode does not remain attached to the electrical conductor after completion of the fusing operation.
Fusing machines are widely used for fusing armature wires to commutator tangs or slots, and stator wires to terminal board contact hooks, of electric motors. A typical armature fusing operation, for example, involves applying a physical force from the fusing electrode to the tang or slot being fused. Next, current is applied to the fusing electrode, which current passes through the commutator to a ground electrode. The resistance of the fusing electrode is higher than that of the commutator, causing the fusing electrode to heat. The heat is thermally transferred to the point of contact between the fusing electrode and the commutator. A similar set of steps is required for stator fusing operations.
Assuming that the fusing process is successfully completed, a reset step is performed wherein the fusing electrode is removed from the electrical conductors and returned to its home position for the next fusing operation. However, various problems can occur during the previously described application of current and heating which may cause the fusing electrode to remain attached to the fused electrical conductors. For example, an excessively worn electrode tip may cause an uneven application of heat which can result in "hot spots" (i.e., excessive application of heat in specific locations) leading to attachment of the electrode. Alternatively, if precise control of the physical and electrical phases of the fusing operation is not maintained, attachment may occur from the application of excess heat.
An apparatus for precise control of the physical phases of the fusing operation is described in Rossi U.S. Pat. No. 5,063,279, entitled "Methods and Apparatus for Fusing Armature and Stator Wires," which is hereby incorporated by reference in its entirety. The application of force from the fusing electrode to the commutator bar (or terminal board) and wires is performed according to predetermined force or displacement functions.
An apparatus for precise control of the electrical phases of the fusing operation is described in applicant's co-pending, commonly-assigned application Ser. No. 07/903,910, filed Jun. 25, 1992, now U.S. Pat. No. 5,300,753, entitled "Methods and Apparatus for Fusing Electrical Conductors," which is hereby incorporated by reference in its entirety. In application Ser. No. 07/903,910, now U.S. Pat. No. 5,300,753, a precise, timed, and controlled delivery of electric current to the fusing electrode of a fusing machine based on predetermined fusing profiles is described. In addition, the delivery of electric current is synchronized with the various phases of the application of force or displacement functions described in U.S. Pat. No. 5,063,279. By synchronizing precise control of the physical and electrical phases of the fusing operation, cohesion joints of increased quality are produced, while the occurrences of electrode attachment are reduced.
It is also possible for a typical fusing operation to utilize heat which is generated via means other than by passing a current through an electrode. For example, ultrasonics may be used to create heat through vibration or heat may be supplied via an external flame. Irrespective of the heat source, fusing operations require that force be applied to the workpiece in conjunction with the heat to form the cohesion joint. And, as previously described, the combination of heat and force may cause the force applying member to become attached to the conductors no matter what the heat source is.
If the fusing electrode (or merely the force producing member) does remain attached to the electrical conductors during the reset step, the movement of the fusing electrode may cause weakening of the cohesion joint between the electrical conductors. In a worst case situation, the weakening can be so severe that it may actually cause the fused joint to break. It is readily apparent that any weakened or broken cohesion joints need to be identified before the damaged parts are incorporated into complete electric machines. Traditional methods for identification require carrying out a destructive test (commonly known as a "click test") which, due to the destructive nature of the test, can only be performed on a statistical basis. Statistically discovered problems will only appear after a significant number of sub-standard products have been produced, and as such, may eventually cause more severe problems due to the progressive nature of fusing operation malfunctions.
Therefore, using traditional identification methods, incorporation of damaged components is likely to occur. Such incorporation will, at a minimum, significantly increase manufacturing costs because: (1) broken parts will not be immediately identified and further downstream assembly costs will be wasted on defective components; and (2) problems with the fusing process will continue and probably worsen, affecting additional components until the problems are properly identified. Possibly even more significant is the fact that damaged cohesion joints may unknowingly be incorporated into finished products, resulting in reduced quality of the completed electric motors.
In an effort to try to achieve high quality fusing, time consuming and complex operations must be undertaken to set up the fusing machine, as well as increased inspections on the fusing components to ensure that worn components are quickly replaced. Such operations could be avoided if a fusing machine could precisely apply various levels of current at the proper time throughout the fusing operation and if a fusing machine could immediately identify fusing electrode attachment. Electrode attachment could be used to signal an operator to intervene and inspect the fusing components. Electrode attachment could also be used to automatically reject the component that was attached to the electrode to prevent its incorporation into a final product, thereby increasing the overall quality of the manufacturing operation. Additionally, the fact that electrode attachment occurred could provide feedback to the previously described precision control systems which would immediately change the fusing parameters to avoid attachment in any additional operations.
It would therefore be desirable to provide a fusing machine which identifies the occurrence of fusing electrode attachment during fusing operations. It would also be desirable to provide a fusing machine which modifies the parameters for precise control of the fusing operation in response to the identification of electrode attachment to produce more reliable cohesion joints during fusing operations. It would also be desirable to provide a fusing machine which does not require constant inspection of the fusing components. It would still further be desirable to provide a fusing machine which automatically rejects components for which electrode attachment is identified.